The NOAA Chesapeake Bay Office’s Fall 2025 Seasonal Summary describes how Bay conditions in September–November differed from average—and how those differences may have affected important species in the Chesapeake. Here are some of the elements discussed in the Fall 2025 Seasonal Summary. For more information, graphs, and discussion, you can access the full scientific document .
Water temperatures this fall were lower than average in much of the Chesapeake Bay—notably in southern portions of the Bay.
Sea surface temperature for September–November 2025, as observed by multiple satellites, relative to the average of this seasonal period 2007–2024.
Surface water temperatures at the York Spit CBIBS buoy September–November 2025 (blue line) relative to the long-term average (2007–2024; red line).
Rainfall amounts around the watershed were generally below average. For example, rainfall in southern Maryland was the third lowest since 2007. Lower precipitation results in lower freshwater flow to the Bay, which leads to higher salinity.
Precipitation data from 2007–2025 for September–November for southern Maryland. Data from NOAA Centers for Environmental Information.
Salinity in some parts of the Bay, including at the Gooses Reef CBIBS buoy, was several PSUs above average throughout the season.
Salinity at the Gooses Reef CBIBS buoy September–November 2025 (blue line) relative to the average at each buoy over this seasonal period 2010–2024 (red line).
Bay’s Living Resources Benefit from Cooler Fall
Striped Bass
Fall’s cooler water temperatures—especially cooler-than-average temperatures as experienced in much of the Bay in 2025—can help striped bass bounce back after summertime heat. Cooler waters in fall also hold more oxygen, which means striped bass are less stressed and less likely to die from diseases that thrive in warm water. This may have been the case in fall 2025.
Cooler waters can change where striped bass spend their time. In fall, striped bass begin to feed heavily on fish like menhaden and silversides to help them store energy for the winter ahead. While slightly cooler water might keep resident fish active and healthy, significantly colder water can trigger an earlier migration of the larger fish that enter the Chesapeake Bay from the Atlantic Ocean.
Menhaden
Cooler water and oxygen conditions in fall let menhaden spend their time near the surface of the Bay. That means they can serve as a reliable, high-energy food source for predators such as osprey and striped bass. According to recreational fishing reports from fall 2025, as waters cooled, menhaden began to exit the tidal rivers and head down the Bay.
Blue Crab
Cooler waters are good for blue crabs for several reasons. Instead of burning calories to stay cool, in cooler waters, blue crabs can focus on building up fat and protein stores needed to survive the winter.
Cooler-than-average temperatures can also affect crabbing. Crabs grow by shedding their shells (molting). If water temperatures in fall are cooler than normal, the time between molts increases. This can mean that fewer crabs reach harvestable size before the season slows down. Cooler temperatures can also trigger an earlier move toward the deeper channels of the mainstem Bay, where they overwinter. This often shifts the best crabbing locations from the shallow rivers and creeks to deeper water sooner than expected.
Oysters
This fall’s cooler temperatures and higher oxygen levels were likely beneficial to oysters. Cooler waters tend to reduce disease prevalence, and more-oxygenated water allows oysters to filter water more effectively, which helps them put more energy into adding weight for the winter. Higher salinity aids reproduction and spat sets, but can also increase disease—but any increase in disease (from higher salinity) may have been offset by the benefits of cooler temperatures.
Looking ahead: La Niña
La Niña is the cool phase of a larger climate cycle known as the El Niño-Southern Oscillation (ENSO). It begins with cooling water in the Pacific Ocean and triggers a chain reaction in the atmosphere that shifts weather patterns across North America.
La Niña conditions started forming in September 2025. In October, NOAA officially issued a La Niña Advisory, confirming that the cool phase was present and expected to persist through the winter. La Niña typically favors near to above-normal winter temperatures for the mid-Atlantic—but also increased variability, including sharp cold snaps and shifts in salinity.
Historically, cold winters and cool, wet springs are good for striped bass. The sharp cold fronts seen in November 2025 may have been beneficial.
Blue crabs may experience more challenges. They spend the winter buried in the mud and are highly sensitive to extreme cold. If this winter brings extreme cold snaps, mortality rates could increase. But higher salinity levels in the winter are generally better for crab survival.
La Niña conditions can alter the coastal currents that push menhaden larvae from the Atlantic Ocean into the nursery areas of the Chesapeake Bay. If late winter is drier than average, it could lead to higher salinity in the tributaries, helping juvenile menhaden survive.